There are many typical uses for high intensity discharge (H.I.D.) lighting fixtures, such as for retail stores, warehouses, commercial buildings, and other uses possessing relatively high ceilings. H.I.D. lighting fixtures have been highly successful due to their extreme amount of output of light. Sources of H.I.D. lighting are mercury vapor, metal halide, and high pressure sodium.
These H.I.D. fixtures typically include a single light source lamp with a solid reflector utilized to direct the light in a downward direction. This reflector is normally a bell shape or conical shape. These prior art reflectors are made of reflective substances such as polished aluminum to enhance the efficiency of the fixture. The single lamp supplies direct light and light reflected off the reflector in a downward direction.
The great quantity of light supplied by these prior art H.I.D. fixtures, combined with a typical 1.5 to 1.7 light coverage criteria, allows for a great light coverage area with fewer fixtures.
The drawbacks to using these prior art H.I.D. light sources are the use of excessive amounts of energy, poor color rendition, diminishing lumen output, no choice of color temperatures, and a lack of high efficiency electronic ballasts to power the H.I.D. light sources.
An alternative prior art source of light has been fluorescent lamped fixtures. These fluorescent lamped fixtures have typically utilized long longitudinally extending cylindrical lamps, which are mounted at or slightly below the ceiling level, parallel to the floor surface. These prior art fluorescent lamp fixtures are usually 1 to 4 tubes of four foot to eight foot lengths per fixture, and these prior art fixtures utilize much lower wattage per fixture than the prior art H.I.D. light fixtures. The fluorescent lamped fixtures illuminate a rectangular area and they are usually placed in rows mounted end to end. The draw back with the prior art fluorescent fixtures is the large quantity of lamp fixtures required and the lack of efficiency. The large quantities of prior art fluorescent fixtures significantly increase the initial installation costs, with no advantage or savings for the increase labor cost, when compared to the installation of prior art H.I.D. light fixtures. The traditional fluorescent lamp also lacks the intensity needed for large spacing for high mounting levels.
New technology has brought about the compact fluorescent lamp bulb, which is a four prong lamp with two sets of joined ends creating a double inverted U effect relative to the base. The normal wattage for these double U-shaped fluorescent lamps is from 5 to 26 wattage per lamp and the double U-shaped fluorescent lamps utilize clip-in socket bases, such as commonly designated as G23, GX23, G23-2, GX23-2, G24d1, G24d2, G24d3, G24q1, G24q2, and G24q3 (Sylvania designation or equal). These U-shaped fluorescent lamps have been designated Dulux S.RTM.,Dulux DS/E.RTM., Dulux D.RTM., and Dulux D/E.RTM. by Sylvania, with comparable equals produced by other manufacturers.
There have been several prior art patents utilizing these double U-shaped fluorescent lamps and socket combinations. Among the prior art patents are U.S. Pat. Nos. 4,520,436; 4,704,664 and 4,922,393 of McNair and, additionally, U.S. Pat. No. 5,197,798 of Tickner. McNair's patents describe light fixtures which utilize only a pair of these small compact lamps, generally 3.4 inches to 7.6 inches in length. The McNair double U-shaped lamps are mounted as to be askew to each other in a reflector which allows light out one end in quantities enough to replace small incandescent lamps (such as 50 W-100 W) in similar incandescent fixture configurations. The reflector in McNair is also designed with openings in its upper sides to allow for the mounting of the socket, and connection of these sockets to the ballasts, which power the double U-shaped fluorescent lamps from outside the confines of the reflector. The complete light fixture package of McNair is further encased in a larger housing to enclose the wiring, ballasts, and sockets.
The usefulness of these McNair fixtures over incandescent fixtures is that the McNair fixtures can replace higher wattage incandescent fixtures with a high percentage reduction of energy usage. Moreover, the lamp life of the McNair double U-shaped fluorescent lamps utilized is longer than incandescent lamps which the McNair lamps can replace.
Another related prior art patent is that of Tickner, wherein a light fixture utilizes a grouping of 26 watt compact fluorescent "Dulux D" double U-shaped lamps, with either 6 lamps, 8 lamp, or 12 lamps per fixture. Single or pairs of lamps are activated by individual ballasts. The lamps in Tickner are mounted in a solid, non-translucent reflector as to direct all light in a downward direction. The socket mounting plates are mounted within the concave reflector from 1/4 to 1/2 the distance from the narrow base opening of the reflector to the wider light emitting output portion of the reflector. By combining this large number of 26 watt compact double U-shaped fluorescent lamps the Tickner fixture can produce as many as 14,400 initial lumens in an eight light configuration and 21,600 lumens in a 12 lamp configuration. These wattages produced by the Tickner device compare evenly with that of a 250 watt metal halide high intensity discharge lamp or a 200 watt high pressure sodium. This low wattage compact fluorescent light fixture of Tickner produces only approximately 69 lumen per watt, which is a significant drawback. The Tickner fixture at it's maximum potential cannot come near the very popular 400 watt metal halide H.I.D. high intensity discharge lamps for production of lumens, which initially producing 36,000 lumens, with a mean of 29,000 lumens.
Tickner also has the additional draw back of creating no uplight which is the beneficial discharge of light above the plane of the bottom outlet of the lamp reflector. Uplight capabilities prevent a dead unlighted area above the upper hemisphere of a reflector and allows for more even distribution of light. With Tickner, optional lighting capabilities are limited because the opaque reflector prevents uplight. The drawbacks of Tickner are shown in a certified test report completed May 5, 1992 by Lighting Sciences Inc., 7830 E. Evans Road, Scottsdale, Ariz., U.S.A., 85260, test report #LSI10775 (exhibit). In this certified report it is noted that the "Dulux D" 26 watt double U-shaped lamps produce 69.23 lumens per watt and that the overall efficiency of the fixture is 79.1%. Additionally, it is noted that little or no candlepower is produced above 75 degrees and virtually none beyond 90 degrees or in the upper hemisphere. All of the findings of this testing are typical of the Tickner patent and configuration.